Low emissivity, or low-e, panels are often formed by depositing a reflective layer (e.g., silver), along with various other layers, onto a transparent (e.g., glass) substrate. The various layers typically include dielectric layers, such as silicon nitride, tin oxide, and zinc oxide, to provide a barrier between the stack and both the substrate and the environment, as well as to act as optical fillers and function as anti-reflective coating layers to improve the optical characteristics of the panel.
Conventional low-e panels using such dielectric layers often form cracks along grain boundaries, especially in applications where the substrate is bent or otherwise shaped. Additionally, conventional low-e panels often demonstrate significant changes in color during heat treatment (or tempering) after the layers (i.e., the stack) are formed on the substrate. As such, the tempered panels appear to have a different color than those that have not been tempered.
One current solution involves the use of silicon nitride layers, with one being immediately adjacent to the substrate and another being on top of the stack (i.e., exposed to the environment). While the silicon nitride layers are relatively stable and provide suitable protection from, for example, sodium diffusion from the substrate and moisture in the environment, the deposition rate of such silicon nitride layers is relatively slow and generally requires the use of other dielectric layers as well, such an tin oxide and/or zinc oxide. As a result, manufacturing costs are increased due to the fact that additional targets are required to deposit additional layers.